Methods and apparatus for color grading with gamut match preview

ABSTRACT

A method for color grading within a component color space associated with a display includes receiving a source image comprising a plurality of pixels, wherein each pixel is associated with a color comprising a plurality of color component values in the component color space, wherein the component color space comprises RGB, and wherein a pixel is associated with a color inside a gamut of the display but outside a gamut of a target media, receiving a color grading signal from a user, modifying the color associated with the pixel from the plurality of pixels in response to the color grading signal, to form a graded image comprising the pixel, wherein the pixel is associated with a graded color comprising a plurality of color component values, displaying the graded image on the display to the user, automatically performing a gamut remapping of the graded color associated with the pixel, to form a gamut remapped image comprising the pixel, wherein the pixel is associated with a gamut remapped color comprising a plurality of color component values, wherein at least one color component value of the graded color is substantially similar to one color component value of the gamut remapped color, and displaying the gamut remapped image on the display to the user, wherein the gamut remapped image comprises a plurality of pixels, wherein each pixel from the plurality of pixels is associated with a color within a gamut of the target media.

BACKGROUND OF THE INVENTION

The present invention relates to color grading. More specifically, thepresent invention relates to methods and apparatus for color grading andgamut matching of displayed images to print media (e.g. film media)

Throughout the years, movie makers have often tried to tell storiesinvolving make-believe creatures, far away places, and fantastic things.To do so, they have often relied on animation techniques to bring themake-believe to “life.” Two of the major paths in animation havetraditionally included, drawing-based animation techniques and stopmotion animation techniques.

Drawing-based animation techniques were refined in the twentiethcentury, by movie makers such as Walt Disney and used in movies such as“Snow White and the Seven Dwarfs” (1937) and “Fantasia” (1940). Thisanimation technique typically required artists to hand-draw (or paint)animated images onto a transparent media or cels. After painting, eachcel would then be captured or recorded onto film as one or more framesin a movie.

Stop motion-based animation techniques typically required theconstruction of miniature sets, props, and characters. The filmmakerswould construct the sets, add props, and position the miniaturecharacters in a pose. After the animator was happy with how everythingwas arranged, one or more frames of film would be taken of that specificarrangement. Stop motion animation techniques were developed by moviemakers such as Willis O'Brien for movies such as “King Kong” (1933).Subsequently, these techniques were refined by animators such as RayHarryhausen for movies including “Mighty Joe Young” (1948) and Clash OfThe Titans (1981).

With the wide-spread availability of computers in the later part of thetwentieth century, animators began to rely upon computers to assist inthe animation process. This included using computers to facilitatedrawing-based animation, for example, by painting images, by generatingin-between images (“tweening”), and the like. This also included usingcomputers to augment stop motion animation techniques. For example,physical models could be represented by virtual models in computermemory, and manipulated.

One of the pioneering companies in the computer-aided animation (CA)industry was Pixar. Pixar is more widely known as Pixar AnimationStudios, the creators of animated features such as “Toy Story” (1995)and “Toy Story 2” (1999), “A Bugs Life” (1998), “Monsters, Inc.” (2001),“Finding Nemo” (2003), “The Incredibles” (2004), “Cars” (2006) andothers. In addition to creating animated features, Pixar developedcomputing platforms specially designed for CA, and CA software now knownas RenderMan®. RenderMan® was particularly well received in theanimation industry and recognized with two Academy Awards®. TheRenderMan® software included a “rendering engine” that “rendered” orconverted geometric and/or mathematical descriptions of objects andforms a two dimensional image.

In film making, after the live-action images are shot, or after animatedimages are rendered, one operation typically performed on such images isknown as color grading or color timing. With color grading, the colorsof the image are typically modified until a certain “look” is desired.For example, a live action scene may be filmed at noon, and with colorgrading, a user could make the images appear as though it were night byincreasing the cooler colors (e.g. blues) in the images. As anotherexample, live action scenes may be filmed out of order throughout a day,and by performing color grading, the colors of the scenes could beadjusted until the light in the proper sequence of scenes is “correct.”Additionally, color grading may be performed on animated features toproduce the same results described above. Color grading of the images ina feature is typically a time-consuming and labor intensive process thatrequires exacting control of the colors in the images. Additionally,color grading is typically an artistic process performed by a skilledartisan known as a colorist.

After frames of a film are color graded and the Director is satisfiedwith the appearance of the images on the computer display, the imagesmay be transferred onto film media for distribution into theaters, ontopaper or plastic media, or the like. As discussed in the above-mentionedpatent application, one issue that arises when transferring imagescomputed and displayed on a computer display, is that the images willlook different on the different types of media, e.g. film in thetheater, DVDs on home theater systems, magazines, etc. Some reasons forthis include that the color gamut and color reproduction of a userdisplay and that the color gamut and color reproduction of differenttarget media are often very different.

With regards to color reproduction (typically non-linear) response offilm media, the inventors recognize that characterization is typicallyindependent of the rendered image. For example, to characterize thecolor response, one or more images having ramped color densities arerecorded onto film stock with a film recorder, and the resultant colordensities of the film are measured. Then, based upon the known colordensity output and the corresponding measured color density, the colorreproduction of the film media is determined.

With regards to matching colors displayed on the display to colors inthe color gamut of film media, the inventors now recognize that it isdesirable to limit the amount of automatic gamut matching so as toreduce unintended side effects.

Automatic approaches are typically used to map colors outside a firstcolor gamut (out-of-gamut) to fit within a color gamut (in-gamut). Oftenthese approaches are characterized by rendering intent. Four commonautomatic methods for performing the rendering intent are known asSaturation, Relative and Absolute Colorimetric, and Perceptual intents.

Automatic approaches are typically used to map colors outside a firstcolor gamut (out-of-gamut) to fit within a color gamut (in-gamut). Oftenthese approaches are guided by rendering intent. Four common renderingintents are known as Saturation, Relative and Absolute Colorimetric, andPerceptual intents.

For motion pictures, a problem with implementations of saturationintents, where the vividness of pure colors are desired to be preserved,is that out-of-gamut colors typically, undesirably change in hue. Forexample, a yellow flower may be turned into an orange flower as a resultof such a color transformation. Accordingly, saturation intentsapproaches to out-of-gamut colors are not typically used for motionpictures (live action, or animation).

A problem with implementations of perceptual mapping intents, where allcolors are remapped to in-gamut colors, is that all colors tend tochange. Additionally, the dynamic range of colors is reduced. As aresult, the colors of a modified image may not appear as vivid orsaturated as was originally intended. Accordingly, perceptual intentsapproaches to out-of-gamut colors are not typically used for motionpictures (live action, or animation) as the resulting images may appeardull.

Implementations of automatic colorimetric (relative or absolute) intentsare more often used in the photographic and motion picture industries.This is because with these techniques, pre-existing in-gamut colors aremaintained (absolutely or relatively with respect to a defined whitepoint), while out-of-gamut colors are pulled in-gamut. Typically, suchcolorimetric intents approaches move out-of-gamut colors towards theneutral axis until an in-gamut color is reached.

FIG. 1 illustrates an example of automatically moving out-of-gamutcolors to in-gamut colors, independent of color grading judgments.Illustrated in FIG. 1 is a two dimensional portion of a color chart 100of blue values plotted against green values. In this example, red valuespoint into the page. Color chart includes a representation of a colorgamut 110 for a first media (e.g. a monitor) and a representation of acolor gamut 120 for a second media (e.g. film) in the color space of themonitor (RGB). Outlined in FIG. 1 are regions 130 representing colorswithin color gamut 110, but out-of-gamut with respect to color gamut120. Additionally, a line 150 represents a projection of a neutral axisupon the blue/green plane. As illustrated, in the color spacerepresentation 160, the neutral axis 170 actually runs equidistantbetween the red, green, and blue axes, from black to white.

In the example in FIG. 1, a color 180 is within region 130, and isout-of-gamut with respect to color gamut 120. With a typical gamut remapusing absolute colorimetric intents, color 180 is moved towards neutralaxis 150 until an in-gamut color is obtained. In this example, the newcolor is indicated by color 190. As an example, color 180 has blue,green coordinates of (0.90, 0.20), and color 190 has blue greencoordinates of (0.60, 0.40). Accordingly, color 180 is more much morebluish than color 190. Other colors, such as color 193 may also be movedtowards the neutral axis, to color 195, as illustrated.

As can be seen in representation 160, a more accurate movement of color180 towards neutral axis 170, also adds a red value to color 180. Thus,for example, color 180 may have red, green, blue (RGB) coordinates of(0, 0.20, 0.90), and color 190 may have RGB coordinates of (0.20, 0.40,0.60). Accordingly, color 180 which is bluish to begin with, is remappedto color 190 that is more pinkish. Thus, even if a colorist specifies adark blue color 180, the gamut remap process will automatically turn thedark blue into a pinkish blue.

A significant drawback to using automatic gamut matching operations isthat it often ruins the painstaking color grading performed by thecolorist. More specifically, as stated above, the color grading ofimages is a function that is typically a time and labor intensiveprocess. Further, this process is typically performed painstakingly by acolor expert/artist who determines where each color should be placed.Accordingly, using automatic gamut matching processes after a colorgrading process will ruin the color grading for the images. As wasillustrated in FIG. 1, working within color gamut 110 of a computermonitor, the color grader may like color 180 and select its value duringthe color grading process. However, as a result of the automatic gamutmatching process, color 180 is automatically remapped to color 190. Asan example, a deep blue of color 180 (e.g. (0, 0.90, 0.20) by the colorgrader may be automatically moved to a pinkish blue of color 190 (e.g.(0.20, 0.60, 0.40), as a result of the automatic gamut matching. Thus ascan be seen, the inventors have determined that such automatic gamutmatching is disadvantageous with regards to color graded images, andthat the automatic gaming matching often “fights” the intentions of thecolor grader.

One technique sometimes used by film makers when is limiting the gamutof a digital intermediate to the film gamut throughout the workflow. Forexample, the universe of colors on the digital display will be anintersection of the film gamut and the display gamut. In such a system,there is no color gamut matching problem when performing film-out, thusgamut matching is not needed when printing to film.

One drawback to such a system is that the film makers are visuallyrestricted to working in the narrow color gamut (i.e. the intersectionof the film gamut and the display gamut). Accordingly, if the film istransferred to DVD for a home theater system or projected digitally on adigital projector, the colorist will not be able to preview the gradingof the resulting images. Another drawback is, there is no way toincrease the color gamut of the film, without repeating the entiredigital workflow. As an example, after a film is mastered for film, ifthe producer wanted to show their film on a digital projection system,the entire digital workflow would have to be repeated. This is becausethe film was not designed for the gamut of the digital projectionsystem, which is typically wider in some respects compared to film. Insuch cases, to re-master for a digital projection system, specialeffects, live action shots, etc. would most likely have to be regraded,to make use of the full gamut of the digital projection system.

In light of the above, what is desired are more efficient ways forperforming color grading and gamut matching, without the drawbacksdescribed above.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to color grading. More specifically, thepresent invention relates to methods and apparatus for color grading ofimages and for mapping of display colors in the images that areout-of-gamut for film.

According to one aspect of the invention, a method for color gradingwithin a component color space associated with a display is disclosed.One technique includes receiving a source image comprising a pluralityof pixels, wherein each pixel is associated with a color comprising aplurality of color component values in the component color space,wherein the component color space comprises RGB, and wherein a pixel isassociated with a color inside a gamut of the display but outside agamut of a target media, and displaying the source image on the displayto the user. A process may include receiving a color grading signal froma user, modifying the color associated with the pixel from the pluralityof pixels in response to the color grading signal, to form a gradedimage comprising the pixel, wherein the pixel is associated with agraded color comprising a plurality of color component values, anddisplaying the graded image on the display to the user. Methods mayinclude automatically performing a gamut remapping of the graded colorassociated with the pixel, to form a gamut remapped image comprising thepixel, wherein the pixel is associated with a gamut remapped colorcomprising a plurality of color component values, wherein at least onecolor component value of the graded color is substantially similar toone color component value of the gamut remapped color, and displayingthe gamut remapped image on the display to the user, wherein the gamutremapped image comprises a plurality of pixels, wherein each pixel fromthe plurality of pixels is associated with a color within a gamut of thetarget media.

According to one aspect of the invention, a computer system is describedembodied as described below.

According to one aspect of the invention, a user interface for acomputer system including a display is described below.

According to yet another aspect of the invention, computer programproduct is provided on a computer-readable tangible media, such as asemiconductor media (e.g. RAM, flash memory), magnetic media (e.g. harddisk, SAN), optical media (e.g. CD, DVD, barcode), or the like thatinstructs a computer-system to operate as described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings.

FIG. 1 illustrates an example of moving out-of-gamut colors according toan absolute colorimetric intents;

FIG. 2 is a block diagram of typical computer system according to anembodiment of the present invention;

FIG. 3 illustrates block diagrams of a system according to variousembodiments of the present invention;

FIGS. 4A-C illustrate a flow diagram of various embodiments of thepresent invention;

FIGS. 5A-D illustrates examples according to embodiments of the presentinvention; and

FIGS. 6A-E illustrate a visual representation of color gamuts matchingaccording to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 2 is a block diagram of typical computer system 200 according to anembodiment of the present invention.

In the present embodiment, computer system 200 typically includes adisplay 210, computer 220, a keyboard 230, a user input device 240,computer interfaces 250, and the like. In various embodiments, display(monitor) 210 may be embodied as a CRT display, an LCD display, a plasmadisplay, a direct-projection or rear-projection DLP, a microdisplay, orthe like. In various embodiments, display 210 may be used to visuallydisplay user interfaces, images, as described below, gamuts, or thelike.

In various embodiments, user input device 240 is typically embodied as acomputer mouse, a trackball, a track pad, a joystick, wireless remote,drawing tablet, voice command system, eye tracking system, and the like.User input device 240 typically allows a user to select objects, icons,text and the like that appear on the display 210 via a command such as aclick of a button or the like. An additional specialized user inputdevice 245 may also be provided in various embodiments. User inputdevice 245 may include a series of rotating knobs, slider switches, orthe like, that provides a user with control of primary color components(e.g. red, green, and blue), as will be described below. In otherembodiments, user input device 245 include additional computer systemdisplays (e.g. multiple monitors). Further user input device 245 may beimplemented as one or more graphical user interfaces on such a display.

Embodiments of computer interfaces 250 typically include an Ethernetcard, a modem (telephone, satellite, cable, ISDN), (asynchronous)digital subscriber line (DSL) unit, FireWire interface, USB interface,and the like. For example, computer interfaces 250 may be coupled to acomputer network, to a FireWire bus, or the like. In other embodiments,computer interfaces 250 may be physically integrated on the motherboardof computer 220, may be a software program, such as soft DSL, or thelike.

In various embodiments, computer 220 typically includes familiarcomputer components such as a processor 260, and memory storage devices,such as a random access memory (RAM) 270, disk drives 280, and systembus 290 interconnecting the above components.

In some embodiments, computer 220 includes one or more Xeonmicroprocessors from Intel. Further, in the present embodiment, computer220 typically includes a UNIX-based operating system.

RAM 270 and disk drive 280 are examples of computer-readable tangiblemedia configured to store data such as source image files, gamuts fordifferent types of print media (e.g., film, paper, plastic, metal, etc.)models including geometrical descriptions of objects, ordered geometricdescriptions of objects, procedural descriptions of models, scenedescriptor files, a rendering engine, embodiments of the presentinvention, including executable computer code, human readable code, orthe like. Other types of tangible media include magnetic storage mediasuch as floppy disks, networked hard disks, or removable hard disks;optical storage media such as CD-ROMS, DVDs, holographic memories, orbar codes; semiconductor media such as flash memories,read-only-memories (ROMS); battery-backed volatile memories; networkedstorage devices, and the like.

In the present embodiment, computer system 200 may also include softwarethat enables communications over a network such as the HTTP, TCP/IP,RTP/RTSP protocols, and the like. In alternative embodiments of thepresent invention, other communications software and transfer protocolsmay also be used, for example IPX, UDP or the like.

In some embodiments of the present invention, a graphical processorunit, GPU, may be used to accelerate various operations, describedbelow. Such operations may include color grading, automaticallyperforming a gamut remapping, or the like.

FIG. 2 representative of a computer system capable of embodying thepresent invention. It will be readily apparent to one of ordinary skillin the art that many other hardware and software configurations aresuitable for use with the present invention. For example, the computermay be a desktop, portable, rack-mounted or tablet configuration.Additionally, the computer may be a series of networked computers.Further, the use of other micro processors are contemplated, such asXeon™, Pentium™ or Core™ microprocessors; Turion™ 64, Opteron™ orAthlon™ microprocessors from Advanced Micro Devices, Inc; and the like.Further, other types of operating systems are contemplated, such asWindows®, WindowsXP®, WindowsNT®, or the like from MicrosoftCorporation, Solaris from Sun Microsystems, LINUX, UNIX, and the like.In still other embodiments, the techniques described above may beimplemented upon a chip or an auxiliary processing board. Variousembodiments may be based upon systems provided by daVinci, Pandora,Silicon Color, or other vendors.

FIG. 3 illustrates block diagrams of a system according to variousembodiments of the present invention. More specifically, FIG. 3illustrates a block diagram including a computer system 300 and a filmrecorder 310. An image 320 is provided to computer system 300, whichoutputs an image 330 to film recorder 310. In turn, film recorder 310records image 400 to film 410. In the present example, image 320 is animage with colors in the color gamut of a display and image 330 is animage with colors in the color gamut of film 410.

In various embodiments, computer system 300 may be embodied asillustrated in FIG. 2 above, including a display 350, a processingsystem 360, gamut remapping data 385, and grading controls 370. In thepresent example, display 350 is used to display images to a user 380,such as image 320 and image 340; grading controls 370 allows user 380 toinput color grading signals after viewing the images on the display; andprocessing system 360 is used to modify the color of the images inresponse to the color grading signals of user 380. As an output, image340 is an image with colors in the color gamut of film 410.

Also illustrated in computer system 300 is a transformation block 390.In various embodiments of the present invention, the colorresponsiveness of film recorder 310 and 410 are characterized. Forexample, in response to a linear ramp of color densities, the film mayrecord a non-linear ramp of color densities. Accordingly, the inverse ofthe color responsiveness of the film 395 is implemented intransformation block 390. In practice in the example above, if image 340includes a linear ramp of color densities, image 330 would include anon-linear ramp of color densities, and image 400 would reflect thelinear ramp of color densities.

In some embodiments of the present invention, transformation block 390may implemented by processor 360 or refer to a data structure stored indedicated look up table (LUT), in the main memory of computer 360, orthe like that provides the reverse transform data.

In various embodiments of the present invention, film recorder 310 maybe any conventional film recorder, such as an Arrilaser film recorder byArri, or the like. In some embodiments, film recorder 310 may be basedupon laser illumination, and image 330 (digital data) is used to controlthe one or more lasers in film recorder 310. In other embodiments, othertypes of transfer of source image digital data to film are contemplated.For example, image 330 my drive a CRT, or the like. In otherembodiments, image 330 may drive one or more illuminated LCD panels.Examples of this are disclosed in co-pending U.S. application Ser. No.10/698,985 filed Oct. 31, 2003. This application is incorporated hereinfor all purposes.

In various embodiments of the present invention, film 410 is exposed tothe lasers or display devices within film recorder 310. In variousembodiments of the present invention, film 410 may be negative filmstock or positive film stock. In some embodiments, the negative filmstock may be used to form an “internegative” or any other type ofnegative (e.g. “master negative”), from which a “release print” may bemade, via contact-printing, or the like. In cases where positive filmstock may be used, a “release print” may be directly made, or an“interpositive” may be made. In various cases, the interpositive may beused to print one or more internegatives, which themselves may be usedto make release prints.

In other embodiments of the present invention, film recorder 310 may beany other type of digital to printed media transfer apparatus. Forexample, the transfer apparatus may print onto media such as papermedia, plastic media, semiconductor media, metal media, or any othertype of media which can be viewed.

FIGS. 4A-C illustrate a flow diagram of various embodiments of thepresent invention. FIGS. 4A-C will be described with reference toelements in FIG. 3 for convenience.

Initially, image 320 (represented as source digital data), is providedto computer system 300, step 500. In various embodiments, image 320 maybe a rendered image, as described above, a live action image (filmed bya digital video camera, filmed on film stock and digitized, or thelike), a combination of rendered and live action images, or the like.

In various embodiments of the present invention, image 320 isrendered/processed within the color space of display 350. In otherwords, the colors within image 320 may all be within the color gamut ofdisplay 350. In some examples the color space of display 350 istristimulus, for example: red, green, and blue (RGB), or the like; inanother example, the color space of display 350 is hexchromatic, forexample, red, green, blue, cyan, magenta, and yellow (RGBCMY); or thelike.

Next, in FIG. 4A, the gamut mapping data 385 from the color gamut ofimage 350 to color gamut of image 410, is retrieved from a memory ofprocessing system 360, step 510. In various embodiments, the color gamutmay be specified by the manufacturer of film 410, or may be determinedempirically. In one example, the color gamut for film 410 is stored withrespect to the color space of the display gamut. Referring back to FIG.1, for example, color gamut 120 represents a two-dimensional slice ofcolors reproducible by film 410, with regards to the color space of themonitor: RGB. In some examples, the color gamut of film 410 may beapproximated via mathematical functions. Typically, the gamut mappingdata 385, described below, may be determined a priori.

In various embodiments, image 320 is displayed on display 350 for thecolorist to view, step 520. In addition, in this step, colors withinimage 320 that are outside the color gamut of film 410 (i.e.out-of-film-gamut) may be highlighted to the colorist. For example,pixels having out-of-film-gamut colors in image 320 may alternativelyblink between the out-of-film-gamut color and another color, such asblack or white. As another example, pixels having out-of-film-gamutcolors may be mapped to a pre-defined color, such as yellow. Many otherways of highlighting pixels having out-of-film-gamut colors in image 320are contemplated, for instance, in some embodiments, the out-of gamutcolors are highlighted on user demand.

In subsequent steps, based upon the highlighted colors, the coloristthen color grades the image, typically while observing the effects onthe color graded image, and sometimes on the gamut remapped image.

More specifically, in various embodiments of the present invention,while viewing image 320 on display 350, the user selects a color orrange of colors, and provides color grading input signals, step 530. Onemethod for proving the color grading input signals is via gradingcontrols 370. As will be described further below, grading controls 370may provide the colorist with channel (e.g. R, G, or B) independentcontrol for moving colors for the color grading process. In someembodiments, grading controls 370 includes a series of knobs, each ofwhich controls a separate color component. For example, one knob maycontrol the red color component, one knob may control the blue colorcomponent, and one knob may control the blue color component. In otherembodiments, any conventional grading methods may be used. In responseto the color grading input signals, the colors of the selected colorsare modified, step 535.

In various embodiments, as described above, while viewing the image inthe display gamut, the colorist provides the color grading input signalsprovided to color grade image 320. As described above, the coloristmodifies the colors on the image to obtain a certain “mood,” to maintainproper color continuity, to change the time of day, or for any otherreason. Accordingly, color grading may include color grading of colorsalready within the gamut of film 410 (i.e. in-film-gamut) and/or mayinclude color grading of colors outside the gamut of film 410 (i.e.out-of-film-gamut).

Next, the gamut remap is applied to the colors of the graded image, toallow the colorist to see how the graded image will appear after thegamut remap, step 540. As discussed above, the gamut remap may changethe colors of the graded image. Accordingly, the colorist views thegraded image, after the image has been remapped into the film gamut, ondisplay 350, step 545. As will be described below, embodiments of thegamut remapping process typically constrains one or more color componentvalues within the given color space. For instance, highly saturated bluecolors (e.g. 0.8) remain blue (e.g. 0.7) after gamut remap, and are notgiven additional red or green component values; as another example, acolor with high (e.g. 0.9) green values, are decreased in green values(e.g. 0.8) without the addition of additional red or blue values.

In various embodiments, if the user is not satisfied with the colorsproduced as a result of the gamut remapping, step 550, the colorist canchange the color grading of the image. An example of this will bedescribed below. If there are other colors to grade, the processdescribed above may be repeated for other colors within or outside thefilm gamut, step 555.

As can be seen, the colorist grades the image for color effect, asdescribed above, and at the same time grades the image taking account ofthe automatic gamut remapping process. In the end, image 340 is colorgraded with respect to the film gamut, step 560.

Next, as illustrated, transformation block 390 typically performs anon-linear transformation of colors in image 340 to form image 330, step570. As was described above, transformation block 390 typically performsan inverse transformation of a transformation inherently performed byfilm recorder 310 and film 410. By performing this inversetransformation, it is expected that by the time image 400 is recorded onfilm 410, image 400 will have the same color linearity (i.e. response)as image 340.

In various embodiments of the present invention, image 330 is thenstored into a memory (e.g. a hard drive, a network storage, opticaldisk), step 580. Next, the process of color grading taking account ofgamut matching, may then be repeated for other images or other scenes,until color grading of the entire feature or work or reel is completed,step 590.

After the color grading has completed, the color graded images of thework may be transferred to a separate storage, step 600. In variousembodiments, the separate storage may be a removable media, such as ahard drive, optical disk, or the like; additionally the separate storagemay be a network storage device, or the like. Accordingly, the colorgraded work may be physically or electronically transferred to a thirdparty, e.g. film lab, or the like, or kept in-house for purposes oftransfer to film.

In some embodiments of the present invention, the color graded images ofthe work are then retrieved from the storage, and input to film recorder310, step 610. As mentioned above, various ways of providing the digitaldata of the color graded images are described including, physicaltransfer and electronic transfer. Next, in response to the digital datarepresenting a color graded image, film recorder 310 transfers image 400to film 410, step 620. As described above, various methods foroutputting the image, including laser, LED, xenon illumination, and thelike are contemplated in various embodiments.

As illustrated in FIGS. 4A-C, this recording process repeats, until allimages of the work or reel have been transferred, step 630.Subsequently, film 410 is developed, step 640. In various embodiments,the developed film 410 represents an internegative copy (e.g. masternegative) of the work or reel, from which release print candidates canbe printed, step 650. Such print candidates may in-turn, be projected ordisplayed to other users (e.g. audience), step 660.

As can be seen from the above, the artistic color grading performed bythe colorist is preserved when transferring the image from display colorspace to the tangible color space (e.g. film media). This is in contrastto the prior art problems illustrated in FIG. 1, where gamut matchingfor film-out distorts the color grading.

FIGS. 5A-D illustrates examples according to embodiments of the presentinvention. FIG. 5A illustrates a user display 700 of an image of ablue-colored object 710. As can be seen, a region 720 is highlighted,representing colors within the display gamut, but not within a filmgamut, e.g. a bright blue region.

In the example in FIG. 5B, using a conventional gamut match process, thehighlighted region 740 of the object 730 is gamut remapped to a pinkishcolor, for the reasons discussed with respect to FIG. 1. As a result,the traditional gamut matching process defeats the intents of the colorgrader—blue becomes pink.

In various embodiments of the present invention, FIG. 5C illustrates atypical display 740, where the colorist grades colors within region 750.Next, embodiments of the gamut matching process described above, areapplied to the graded image, and the colorist views the results ondisplay 760 in FIG. 5D. Specifically in this example, the colorist viewsregion 770 to see if it remains the blue-color desired, or not. If not,the colorist may re-grade colors in region 720 and repeat the process.

FIGS. 6A-E illustrate a visual representation of color gamuts matchingaccording to embodiments of the present invention.

FIG. 6A illustrates a concept according to some embodiments of thepresent invention. More specifically, in FIG. 6A, a two-dimensionalportion 800 of a display color space is illustrated. In cases where thefilm color gamut 810, for example, is smaller than the display gamut 820in a particular color component, some or all of the colors withindisplay gamut 820 may be compressed. As illustrated, the compression mayor may not be linear. In the examples shown, it can be seen that thelower 33% portion 830 of display gamut 820, may or may not becompressed, to occupy the lower 40% portion 840 of film gamut 810; themiddle 33% portion 850 of display gamut 820, may be compressed to occupythe middle 20% portion 860 of film gamut 810; and the top 33% portion850 of display gamut 820, may be compressed to occupy the top 15%portion 860 of film gamut 810. In other embodiments, as illustrated inthe bottom lattice structure, the first and second portion of the gamutare not squashed, laterally, whereas the right most portion of thelattice is squashed in light of the gamut remap. In various embodiments,the ordinality of colors within the original image are preserved in theremapped image. In light of the present disclosure, one of ordinaryskill in the art will recognize that may other types of compressionschemes can be used in various embodiments.

FIG. 6B illustrates one example of a display gamut 890 versus a tangiblemedia gamut (e.g. film gamut) 900. As can be seen in this example,out-of film gamut colors include colors with large blue components,region 910; colors with large red, but small green components, regions920; colors with large green, but small red and green components,regions 930; and the like. Examples of mapping with theses regions 910,920, 930, will be illustrated below.

FIG. 6C illustrates a two-dimensional cross-section 940 of display gamut890 versus film gamut 900. More specifically, cross-section 940illustrates blue versus green components, with red held constant. Itshould be understood from this example, that cross-section 940 mayillustrate a cross-section for virtually any value of the red colorcomponent. In this example, as can be seen, the color components ofcolors within the target gamut are substantially maintained. However,colors outside the target gamut are compressed.

In this example, a color 950, within display gamut 890, but not filmgamut 900, represents a color that has a large blue color componentvalue. In various embodiments of the present invention, the automaticgamut mapping, discussed in step 535, moves color 950 only with respectto one color component, to color 960. In other words, the value of onlyone color component is modified in some embodiments of the presentinvention. In this example, for example color 950 may have RGB values of{0, 0.2, 0.90}, and color 960 may have RGB values of {0, 0.2, 0.5}. Ascan be determined, although the amount of blue is decreased as a resultof the gamut match, color 960 does not become pinkish, as color 190 didin FIG. 1, with RGB values of {0.20, 0.40, 0.60}.

In this example, a color 970, within display gamut 890, but not filmgamut 900, represents a color that has a large green color component,but small blue color component. In various embodiments of the presentinvention, the automatic gamut mapping, discussed in step 535, movescolor 970 only with respect to one color component, to color 980. Inother words, the value of only the green color component is modified invarious embodiments of the present invention. In this example, forexample color 970 may have RGB values of {0.3, 0.8, 0.10}, and resultinggamut matched color 980 may have RGB values of {0.3, 0.7, 0.1}.

In other embodiments of the present invention, a gamut remap may modifyvalues of two color components. For example, in the example in FIG. 6C,color 950 may be remapped to color 970. One theory for such embodimentsis to approximately maintain the color component ratio between at leasttwo color components. Thus, for example, color 970 may have RGB valuesof {0, 0.1, 0.5}. In still other embodiments, a gamut remap may modifyvalues of three color components.

FIG. 6D illustrates a two-dimensional cross-section 990 of display gamut890 versus film gamut 900. More specifically, cross-section 970illustrates red versus green components, with blue held constant. Itshould be understood from this example, that cross-section 970 mayillustrate a cross-section for virtually any value of the blue colorcomponent.

In this example, a color 1000, within display gamut 890, but not filmgamut 900, represents a color that has a large green color component,but small red color component. In various embodiments of the presentinvention, the automatic gamut mapping, discussed in step 535, movescolor 1000 only with respect to the green component, to color 1010. Inthis example, for example color 1000 may have RGB values of {0.2, 0.8,0.4}, and resulting gamut matched color 1010 may have RGB values of{0.2, 0.7, 0.4}.

In this example, a color 1020, within display gamut 890, but not filmgamut 900, represents a color that has a large red color component, butsmall green color component. In various embodiments of the presentinvention, the automatic gamut mapping process moves color 1020 onlywith respect to the green component, to color 1030. In this example, forexample color 1020 may have RGB values of {0.9, 0.1, 0.4}, and resultinggamut matched color 1100 may have RGB values of {0.8, 0.1, 0.4}.

FIG. 6E illustrates a two-dimensional cross-section 1040 of displaygamut 890 versus film gamut 900. More specifically, cross-section 10400illustrates red versus blue components, with green held constant. Itshould be understood from this example, that cross-section 1040 mayillustrate a cross-section for virtually any value of the green colorcomponent. This embodiment illustrates a case where all colors areshifted according to the target gamut. It should be understood thatartistic considerations may be considered in determining whether topreserve original colors that are in-gamut of the target color space, orto remap them. FIGS. 6C and 6D show examples of not substantiallyshifting of such colors, and FIG. 6E shows an example of shifting ofsuch colors. In various embodiments, combinations of these principlesmay be applied with respect to different pairs of color components, orthe like.

In this example, a color 1050, within display gamut 890, but not filmgamut 900, represents a color that has a large predominately blue colorcomponent. In various embodiments of the present invention, theautomatic gamut mapping process described above moves color 1050 onlywith respect to the blue component, to color 1060. In this example, forexample color 1050 may have RGB values of {0.6, 0.2, 0.9}, and resultinggamut matched color 1060 may have RGB values of {0.6, 0.2, 0.8}.

In this example, a color 1070, within display gamut 890, but not filmgamut 900, represents a color that has a large predominately red colorcomponent. In various embodiments of the present invention, theautomatic gamut mapping process described above moves color 1070 onlywith respect to the red component, to color 1080. In this example, forexample color 1070 may have RGB values of {0.9, 0.1, 0.5}, and resultinggamut matched color 1080 may have RGB values of {0.8, 0.1, 0.5}.

In this example, a color 1090, within display gamut 890, but not filmgamut 900, represents a color that has a large red and blue colorcomponents. In various embodiments of the present invention, theautomatic gamut mapping process described above moves color 1070 withrespect to both the red and blue components, to color 1100. In thisexample, for example color 1070 may have RGB values of {0.9, 0.8, 0.9},and resulting gamut matched color 1060 may have RGB values of {0.8, 0.8,0.8}.

In various of the above embodiments, movement of colors outside thegamut of the print media are not necessarily visually pleasing. This isin contrast to the automatic gamut matching schemes described in thebackground, where the goal was to obtain the most visually pleasingimages. It was surprising to the inventors of the present invention thatproviding users (colorists) with the ability to perform less than“pleasing” color grading remappings is actually more powerful for thecolorist. More specifically, providing independent color componentcontrol for gamut remapping to a colorist, actually allows better colorgrading control than previously allowed in systems described in FIG. 1.

Further embodiments can be envisioned to one of ordinary skill in theart after reading this disclosure. For example, other representations ofcolor space for the display and media are contemplated, such as CMY

It should be noted that color grading of out-of-film gamut colors neednot be performed such that the colors are necessarily within the filmgamut. Instead, grading may be performed until the colorist is pleasedwith the color graded image after the gamut remapping process isperformed. In other words, grading repeats until the colorist issatisfied with colors of the image that will be recorded on the tangiblemedia (e.g. film media), although the colors of the image after gradingmay still be outside of the film gamut.

Various embodiments described above illustrate transferring displayedimages to film media, however it should be understood that embodimentsmay also apply to color grading of transferring displayed images ontopaper, metal, glass, or the like.

In other embodiments, combinations or sub-combinations of the abovedisclosed invention can be advantageously made. The block diagrams ofthe architecture and graphical user interfaces are grouped for ease ofunderstanding. However it should be understood that combinations ofblocks, additions of new blocks, re-arrangement of blocks, and the likeare contemplated in alternative embodiments of the present invention.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the invention asset forth in the claims.

1. A method for color grading within a component color space associatedwith a display comprises: a) receiving a source image comprising aplurality of pixels, wherein each pixel is associated with a colorcomprising a plurality of color component values in the component colorspace, wherein the component color space comprises RGB, and wherein apixel is associated with a color inside a gamut of the display butoutside a gamut of a target media; b) receiving a color grading signalfrom a user; c) modifying, using a processor, the color associated withthe pixel from the plurality of pixels in response to the color gradingsignal, to form a graded image comprising the pixel, wherein the pixelis associated with a graded color comprising a plurality of colorcomponent values; d) displaying the graded image on the display to user;e) automatically performing, using the processor, a gamut remapping ofthe graded color associated with the pixel, to form a gamut remappedimage comprising the pixel, wherein the pixel is associated with a gamutremapped color comprising a plurality of color component values, whereinat least one color component value of the graded color is substantiallysimilar to one color component value of the gamut remapped color; and f)displaying the gamut remapped on the display to the user, wherein thegamut remapped image comprises a plurality of pixels, wherein each pixelfrom the plurality of pixels is associated with a color within a gamutof the target media.
 2. The method of claim 1 further comprising: g)receiving another color grading signal from a user; h) modifying thecolor associated with the pixel from the plurality of pixels in responseto the other color grading signal, to form another graded imagecomprising the pixel, wherein the pixel is associated with anothergraded color comprising a plurality of color component values; i)displaying the other graded image on the display to the user; j)automatically performing a gamut remapping of the other graded colorassociated with the pixel, to form another gamut remapped imagecomprising the pixel, wherein the pixel is associated with another gamutremapped color comprising a plurality of color component values, whereinat least one color component value of the other graded color issubstantially similar to one color component value of the other gamutremapped color; and k) displaying the other gamut remapped image on thedisplay to the user.
 3. The method of claim 2 further comprising:repeating steps g)-k) until the user is satisfied with the other gamutremapped image.
 4. The method of claim 1 further comprising: inversetransforming the color values of pixels in the gamut remapped image toform a transformed image comprising a plurality of pixels associatedwith a plurality of transformed color values adapted to drive a filmrecorder; and wherein the target media comprises film media.
 5. Themethod of claim 4 further comprising driving a film recorder with theplurality of transformed color values to record an image onto the filmmedia.
 6. The method of claim 1 wherein ordinality of colors in the onecolor component in the source image are preserved in colors in the onecolor component in the gamut remapped image.
 7. The method of claim 1wherein at least two color component values of the graded color issubstantially similar to two color component values of the gamutremapped color.
 8. The method of claim 1 wherein automaticallyperforming the gamut remapping comprises: determining a preferentialcolor component associated with the graded color; and adjusting only thepreferential color component associated with the graded color todetermine the gamut remapped color.
 9. A method for matching colors in asource image associated with a first color space gamut to a target imageassociated with a second color space gamut, comprising: receiving thesource image; determining, using a processor, a respective at least onepreferential color component for colors within the first color spacegamut but not within the second color space gamut; adjusting, using theprocessor, the colors within the first color space gamut but not withinthe second color space gamut in the direction of the respective onepreferential color component, wherein ordinality of colors within thefirst color space gamut but not within the second color space gamut arepreserved; and determining, using the processor, a resulting image inresponse to the colors within the first color space gamut but not withinthe second color space gamut that were adjusted, and in response to thesource image.
 10. A method for forming a target image comprises: a)receiving a source image; b) receiving color grading adjustment signalsfrom a user to grade the source image within a target gamut; and c)adjusting, using a processor, colors in the source image that are notwithin the target gamut in a preferential direction, to form a targetimage.
 11. The method of claim 10 wherein the preferential direction isin only one color component direction of the target image color space.12. The method of claim 10 wherein the preferential direction is in onlytwo color component directions of the target image color space.